Double-Edge (Doubles in power due to ability, Heals from recoil every turn due to @Leftovers and Aqua Ring, Good offensive move, Good accuracy)

Dig (Helps evade attacks, Doubles in power due to ability, Coverage against Fire-Types, Rock-Types, Electric-Types, and Poison-Types) [And I think Ice-Types, but I could be wrong]

Muddy Water or Ice Punch (Muddy Water - STAB, Doubles in power due to ability, Decent accuracy, Lowers target's accuracy, Coverage against Fire-Types, Ground-Types, and Rock-Types) or (Ice Punch - Good accuracy, May freeze the target, Doubles in power due to ability, Coverage against Grass-Types, Flying-Types, Dragon-Types, and Ground-Types)

**Try to avoid the move Skill Swap because it'll reverse the effect of the ability Huge Power.

I am not kidding. Azumarill is ridiculously powerful right now. I feel that it is one of the most buffed Pokemon this Generation. Just switch in on something that you can force out or cannot threaten you, set up with Belly Drum, and then proceed to utterly destroy your opponent. 244 HP EVs give you 206 Health at lv 50 and 402 Health at lv100.

After a Belly Drum, your health will hit 50%, and Sitrus Berry activates to heal 25% HP. If done right, you now have a beast with +6 of essentially 436 ATTACK (After the Huge Power boost) with 75% HP to spare. Proceed to spam Aqua Jet, squish Dragons with Play Rough, and obliterate Ferrothorn and Skarmory (after Sturdy's broken) with Superpower. If you dont like Superpower's attack and defence drops, you can go with Waterfall instead.

There you go. The wrath of BellyJet Azumarill. The other EVs are put into both Defences to give Azumarill the bulk to get off a Belly Drum.

This moveset is unexpected! Defensive azumarill! :D I use this A LOT in competitive and she tanks hits AMAZINGLY! Aqua ring is even more healing along with the leftovers. Toxic is, well, toxic. which is pretty much a good move on ANY defensive 'mon! protect is to stall EVEN MORE and Hydro pump, Surf or scald will be your STAB move in case you're taunted. Hydro pump has good power but a shaky accuracy and not so good PP. Surf is a good move all round, and Scald can burn.